Calcining fluid coke



Nov. 8, 1966 JAHNIG ET AL 3,284,317

CALCINING FLUID COKE Filed June 19, 1963 Charles E Juhnig Edward J. Gornowski 'nvenfors Patenr Ahorney Patented Nov. 8, 1966 3,284,317 CALCINING FLUID COKE Charles E. Jahnig, Rumson, and Edward J. Gornowsk Cranford, N.J., assignors to Esso Research and Englneering Company, a corporation of Delaware Filed June 19, 1963, Ser. No. 289,054 Claims. (Cl. 201-17) This invention relates to calcining coke particles to improve their quality, and more particularly, relates to calcining fluid coke particles to increase their density and reduce their resistivity. In cases where the coke particles contain large amounts of sulfur, desulfurization of the coke particles may be carried out using the process of the present invention.

A commercial fluid coking process is in use where the oil feed to the process is a heavy residual petroleum oil and is a low grade stock. The coking process produces liquid and gaseous hydrocarbons and fluid coke particles. There is a large market for petroleum coke for the production of electrodes in aluminum manufacture. Usually the coke particles need further treatment to increase their density and reduce their resistivity. In some cases, where the sulfur content of the coke particles is too high, it is necessary to desulfurize the coke particles.

According to the present invention, coke particles are calcined by flowing or passing the coke particles down an inclined graphite air or gas slide type of system which is heated by electric resistance heating. The rate of heating is easily controlled by regulating the hold up of coke on the air or gas slide and this in turn can be done by changing the angle of inclination, by adding baflles or weirs to the slide, by varying or pulsing the aeration gas, etc.

In the drawing:

FIG. 1 represents a vertical longitudinal cross section of one form of apparatus adapted to practice the present invention;

FIG. 2 rep-resents a top plan view of the apparatus shown in FIG. 1; and

FIG. 3 represents a vertical transverse cross section taken substantially on line 33 of FIG. 2.

Referring now to the drawing, the reference character designates an inclined air or gas slide which is provided with a cover or enclosure 12 to exclude 'air and to collect the oil gas produced during calcination. The gas produced during calcining is withdrawn overhead through line 14. The air or gas slide 10 is shown as having one end resting on the ground or on an insulated surface 16. The air or gas slide 10 is held in an adjustable inclined position in any conventional manner. One means diagrammatically shown to support the other end of air or gas slide includes an insulating block 18 secured to the bot-tom of the air or gas slide and having an arm 22 pivotally mounted at 24 to block 18. Stops 26 are provided on the ground in spaced relation to afford abutrnents for the lower end of arm 22 to change the height of the lifted end of the air or gas slide and thereby to change the angle of incline of the air or gas slide.

As shown in FIG. 3, the air or gas slide 10 is channeled or U-s'haped in vertical cross section and provided with cover 12. The slide 10 is preferably made of graphite, or

other electrical conducting material such as silicon can hide, etc. Electricity is applied through electrodes 28 and 30 secured to the base of the slide 10. Parallel to the bot tom 32 of the U-shaped slide 10 and a Sl'lOIt distance above the bottom 32 is a grid or preferably a graphite porous plate 34 to permit flow of fluidizing gas therethrough. Fluidizing gas, such as hydrogen, nitrogen, or the like, is introduced into the bottom of the channel or U-shaped slide below porous plate 34 through line 36. Preferably, part of the hydrogen-containing gas formed during calcination of the coke is recycled as the fluidizing gas, purified if necessary to avoid plugging grid 34. The porous plate is heated by electricity introduced by means of electrodes 28 and 30.

Or the slide 10 may be made of refractory material which does not conduct electricity and the electric contacts 28 and 30 are connected to graphite porous plate 34 or are made in a way to direct most of the electric current flow through plate 34 to directly heat the plate which is in direct contact with the coke particles for best heat transfer.

The slide 10 has upstanding ends 38 and 40. The end 40 adjacent the lower end of slide 10 acts as an abutment over which the calcined coke particles rnust flow to leave the calcining slide 10.

The coke particles are of a size between about 10 and 325 mesh, preferably between about 20 and200 mesh. The process and apparatus are especially adapted foruse with fluid coke made by the commercial fluid coke process shown in Pfeiffer et a1. Patent 2,881,130, granted April 7, 1959, but other petroleum or other cokes may be used provided they are of flu-idizable size or are free flowing.

Fluid coke particles from the burner unit of a fluid coking unit at a temperature between about 1000 F. and 1800 F. are introduced into funnel-shaped feeding inlet 42 which extends through cover 12 and has its lower end 44 arranged to discharge coke above the porous plate 34. Fluidizing gas such as nitrogen or hydrogen is introduced through line 36 into the space 46 below porous plate 34 for passage through plate 34 to fluidize the coke particles on porous plate to form fluid bed 48 and to cause the coke particles to flow down the in clined porous plate 34. The gas passes up through the fluidized bed 48 of coke particles at a superficial velocity between about .01 and .5 feet/second, preferably .05 to .2 feet/ second.

To supply heat during calcination, electricity of a potential of 0.1 to 10 volts per inch (depending on design and material of construction of plate 34) is passed through plate 34 to heat perforated plate 34 to a temperature between about 2000 and 3000 F. and to heat the coke particles to a calcining temperature, for example, between about 2200" F. to 2400 F. The coke particles are heated both by electrical resistance and by conduction from plate 34. The fluidizing gas is heated in passing through the electrically heated porous plate 34. The coke particles are maintained at a calcination temperature above about 2000 F. fora time between about A and 5 minutes, and preferably not less than about 1 minute. The time of heating can be controlled by regulating the hold up of coke on the slide by changing the angle of inclination of the slide 10 by changing the position of pivoted arm 22, and by controlling the pattern of electric resistance along plate 34 by varying the width, thickness, etc. The coke particles will flow with an inclination of 5 or less. A maximum angle with the horizontal is usually about 45 As the angle is increased, less gas is needed to insure flowof solids, but residence 'time'fis reduced. Other means such as baflies or wcirs or the like may be used. Instead of an inclined slide, a horizontally arranged slide may be used.

During calcination, gases including hydrogen and methane are driven off from the coke particles. The off gas comprises mostly hydrogen and is withdrawn through overhead line 14. Part of the hydrogen-containing gas from overhead line 14 may be used as the fluidizing gas introduced into line 36. The rest is recovered for use as hydrogen or fuel.

The hot calcined coke particles arriving at the bottom end of slide 10 pass over or overflow abutment 40 into receiving chamber 52 which is also enclosed to prevent access of air. The hot calcined coke particles may be passed to funnel-shaped discharge member 54, then cooled or quenched with water, etc., and passed to storage.

In one example using a gas slide type system, the slide 10 was held at an angle of about from the horizontal. The slide was constructed from a 5" diameter electrode and was about 4 feet long from abutment 38 to abutment 40. The grid34 was made of commercially available porous graphite. The fluidizing gas was nitrogen or argon and was introduced into space 46 under grid 34 at a rate to give a superficial gas velocity in fluid bed 48 of about 0.1 foot/second. The slide was enclosed.

The feed coke at a temperature of about 100 F. was coke from a fluid coking process having a size between about 30 and 200 mesh and was fed at a rate of about 5 pounds per hour. The electricity supplied was about 1 volt per inch and was sufficient to heat the coke particles to a temperature of about 2400 F. The coke particles were heated for about 1 minute to attain 2400 F. The coke particles were then cooled by holding in an enclosed chamber.

The following Table I compares the characteristics of coke particles calcined in a muffle furnace and in an apparatus according to the present invention.

TABLE I Muflle Air Slide Time Several 1 Min 10 Mins.

Hours Coke A:

Percent Sulfur 3. 65 6.12 4. 56 Percent Volatile Matter- 06 26 11 Real Density, g./cc 1.88 1. 84 1. 85 Bulk Density, g./ce 1. 10 1. 10 1. 11 Coke B:

Percent Sulfur 1. 44 1. 40 1. 13 Percent Volatile Matter- 20 24 07 Real Density, g./ce 1.97 1. 87 1. 97 Bulk Density, g./cc 1.03 94 .97 Coke 0:

Percent Sulfur 2. 48 2. 51 2. 44 Percent Volatile Matter 16 60 20 Real Density, g./ce 1. 92 1. 96 1. 94 Bulk Density, g./cc 1. 16 1.12 1. l4 Coke D:

Percent Sulfur 3. 57 4. 69 3.97 Percent Volatile Matter 14 35 20 Real Density, g./cc 1. 94 1. 89 1.90 Bulk Density g./ce 1. 16 1. 10 1.09

The calcined fluid coke was used in making test electrodes by using 75% by weight of fluid coke regular size and 25 weight percent coke fines having 40% smaller than 325 mesh, and 18 weight percent coal tar pitch binder. The electrodes were baked in 48 hours, including 2 hours at 2000 F.

The following table compares the resulting data:

These results show that the air slide type electrically heated calciner produces a good grade of coke for electrode manufacture.

The rate of heating the coke particles should not be done too fast. The coke particles should be heated to 2400 F. in about one minute or more. When the heating is faster, it is found that the coke particles develop cracks and makea poor electrode. This is not associated with release of volatile material, since a coke sample that was devolatilized at 1500 F. gave the poor quality when rapidly heated to 2400 F. in about one second. The poor quality of the coke is associated with the inherent shrinkage of low temperature coke when it is rapidly heated from, say, 1500 F. to 2400 F. in less than one minute. When a longer heating time, say, 10 minutes was taken to heat the coke particles to 2400 F. or higher, then the calcined coke product was acceptable for electrode manufacture.

What is claimed is:

1. A method of calcining fluid petroleum coke particles of a size between about 10 and 300 mesh which comprises introducing such coke particles into the upper end of an enclosed inclined gas slide type calcining zone above a porous inclined electrical resistance heating grid, introducing fluidizing gas into the bottom portion of said calcining zone and passing it up through said porous grid to fluidize said coke particles and move them down along the inclined calcining zone, passing electric current through said grid to heat said porous grid and to heat the coke particles thereon to a temperature between about 2000 F. and 2400 F. for about 1 to 5 minutes as the coke particles move down over said grid and through said inclined calcining zone, withdrawing calcined coke particles from the lower end of said incline-d calcining zone as product and removing gaseous material overhead from said calcining zone.

2. A method according to claim 1 wherein the angle of inclination from the horizontal of said inclined calcining zone is between about 2 and 10.

3. A method according to claim 1 wherein the angle of inclination from the horizontal of said inclined calcining zone is changed to vary the time of calcining of the coke particles passing through said calcining zone.

4. An apparatus including a gas slide provided with an enclosing top member to form a chamber, said gas slide being arranged at an angle to the horizontal and including a graphite electrical resistance heating porous plate forming the floor in said chamber, said porous plate also being arranged at an angle to the horizontal and being spaced from the bottom of said chamber, means for feeding solid particles onto the upper end of said porous plate in said chamber, means for introducing fluidizing gas into the bottom of said chamber below said porous plate for passage up through said porous plate to fluidize solids on said plate, means for electrically heating said graphite porous plate to heat the solids thereon, withdrawal means at the other end of said chamber for withdrawing treated solids and a pipe leading from the top of said chamber to remove gases driven oif from the solids during heating.

' 5. An apparatus according to claim 4 wherein means are provided whereby the angle of inclination of said chamber may be varied to vary the rate of flow of solids over said inclined porous plate and down through said chamber.

References Cited by the Examiner UNITED STATES PATENTS 2,717,867 9/1955 Jewell et al 201-31 X 2,743,218 4/1956 Herrmann 20117 X 3,086,923 4/1963 Destremps et a1 20117 FOREIGN PATENTS 607,474 10/1960 Canada.

MORRIS O. WOLK, Primary Examiner.

1 JOSEPH SCOVRONEK, Examiner. 

1. A METHOD OF CALCINING FLUID PETROLEUM COKE PARTICLES OF A SIZE BETWEEN ABOUT 10 AND 300 MESH WHICH COMPRISES INTRODUCING SUCH COKE PARTICLES INTO THE UPPER END OF AN ENCLOSED INCLINED GAS SLIDE TYPE CALCINING ZONE ABOVE A POROUS INCLINED ELECTRICAL RESISTANCE HEATING GRID, INTRODUCING FLUIDIZING GAS INTO THE BOTTOM PORTION OF SAID CALCINING ZONE AND PASSING IT UP THROUGH SAID POROUS GRID TO FLUIDIZE SAID COKE PARTICLES AND MOVE THEM DOWN ALONG THE INCLINE CALCINING ZONE, PASSING ELECTRIC CURRENT THROUGH SAID GRID TO HEAT SAID POROUS GRID AND TO HEAT THE COKE PARTICLES THEREON TO A TEMPERATURE BETWEEN ABOUT 2000*F. AND 2400*F. FOR ABOUT 1 TO 5 MINUTES AS THE COKE PARTICLES MOVE DOWN OVER SAID GRID AND THROUGH SAID INCLINED CALCINING ZONE, WITHDRAWING CALCINED COKE PARTICLES FROM THE LOWER END OF SAID INCLINED CALCINING ZONE AS PRODUCT AND REMOVING GASEOUS MATERIAL OVERHEAD FROM SAID CALCINING ZONE. 